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Monday, September 11, 2017

Weekly Propagation Forecast Bulletins

Product: Weekly Highlights and Forecasts
:Issued: 2017 Sep 11 0813 UTC# Prepared by the US Dept. of Commerce, NOAA, Space Weather Prediction Center# Product description and SWPC web contact http://www.swpc.noaa.gov/weekly.html## Weekly Highlights and Forecasts#Highlights of Solar and Geomagnetic Activity 04 - 10 September 2017
Solar activity was at moderate to high levels. Moderate levels were observed on 09 Sep while high levels were observed for the rest of the period. Region 2673 (S09, L=119, class/area Dkc/1060 on 08 Sep) quickly overtook Region 2674 (N14, L=103, class/area Fhc/930 on 03 Sep) in terms of area and magnetic complexity. Region 2673 maintained a very active beta-gamma-delta magnetic group from 04 Sep until it rotated onto the western limb on 10 Sep. This region managed to produce a total of 54 C-flares, 26 M-flares, and 4 X-flares. On 04 Sep, there was an M5/3b flare (R2-Moderate) at 04/2033 UTC with an associated 2100 sfu Tenflare, Type II (estimated velocity 1,472 km/s) radio sweep, and an asymmetric full halo CME first observed in SOHO/LASCO C2 imagery at 04/2048 UTC. On 06 Sep, there was an X9/2b flare (R3-Strong) that occurred at 06/1202 UTC with an associated 14,000 sfu Tenflare, Type II (estimated velocity 1,765 km/s) and Type IV radio sweeps, and an asymmetric full halo CME first observed in SOHO/LASCO C2 imagery at 06/1224 UTC. On 10 Sep, an X8 flare (R3-Strong) occurred at 10/1606 UTC with an associated 1,900 sfu Tenflare, Type II (estimated velocity 928 km/s) and Type IV radio sweeps and an asymmetric full halo CME first observed in SOHO/LASCO C2 imagery at 10/1600 UTC. A magnetic crochet was observed on solar-facing magnetometers during the X8 flare as well as an EIT wave propagating across the solar disk in SDO/EUV 193 imagery beginning at 10/1557 UTC. The CMEs observed on 04 and 06 Sep was determined to have Earth-directed components. The 10 Sep CME had an estimated plane-of-sky speed around 2,100 km/s; however the bulk of the CME was not Earth-directed. Analysis is still on-going for the event.

The M5 flare on 04 Sep and X9 flare on 06 Sep caused an enhancement in the greater than 10 MeV proton flux above the 100 pfu (S2-Moderate) threshold. The enhancement reached the 10 pfu(S1-Minor) threshold at 05/0040 UTC, crossed the 100 pfu threshold at 05/0715 UTC, reached a maximum of 844 pfu at 08/0035 UTC, crossed below the 100 pfu threshold at 08/0620 UTC, and ended at 09/0005 UTC. Another enhancement in the 10 MeV protons and 100 MeV protonsoccurred with the X8 flare on 10 Sep. The greater than 10 MeV protons increased above the 10 pfu threshold at 10/1645 UTC, crossed the 100 pfu threshold at 10/1705 UTC, and crossed the 1000 pfu(S3-Strong) threshold at 10/1840 UTC. The 100 MeV proton event above 1 pfu began at 10/1625 UTC and reached a maximum of 68 pfu at 10/2215 UTC. The greater than 10 MeV protons are currently above the 1000 pfu threshold at the time of this report. The greater than 2 MeV electron flux at geosynchronous orbit reached high levels throughout the period with a maximum flux of 15,800 pfu observed at 04/1805 UTC.

Geomagnetic field activity ranged from quiet to severe (G4) storm levels. Solar wind parameters began the period under the diminishing influence of a positive polarity coronal hole high speed stream (CH HSS) from 04-06 Sep. Solar wind speed ranged from 430 to 680 km/s with total field between 3-9 nT. The geomagnetic field was at Quiet to G1 (Minor) storm levels on 04 Sep and quiet to active levels on 05-06 Sep. Late on 06 Sep, the first of two CMEs were observed. The first CME, associated with the M5 flare on 04 Sep, was first observed passing the DSCOVR spacecraft at 06/2308 UTC. Total field increased to 16 nT at 06/2324 UTC and solar wind increased to a maximum of 610 km/s at 06/2309 UTC. The Bz component was mostly north for this event with minor fluctuations to -10 nT. Then on 07 Sep, the second CME reached the DSCOVR spacecraft further increasing total field to a maximum of 34 nT at 07/2254 UTC while the Bz component deflected southward for nearly 5 hrs. reaching a maximum of -32 nT. Solar wind increased to a maximum of 842 km/s at 08/0848 UTC before slowly decreasing to near 530 km/s by 10 Sep. Total field increased once more at 08/1121 UTC to a maximum of 18 nT while the Bz component went southward to a maximum of -17 nT. The Bz component stayed mostly negative throughout the rest of the day on 08 Sep.

Geomagnetic sudden impulses of 21 nT (Fredericksburg magnetometer) were observed at 06/2348 UTC and 70 nT at 07/2304 UTC with the arrival of both CMEs. The geomagnetic field responded with quiet to G4 (severe) storm levels on 07 Sep, active to G4 (severe) storm levels on 08 Sep, quiet to unsettled levels on 09 Sep, and quiet to active levels on 10 Sep.

Forecast of Solar and Geomagnetic Activity 11 September - 07 October 2017
Solar activity is expected to be at R1-R2 (Minor to Moderate) levels on 11 Sep as Region 2673 rotates further around the west limb. A decrease to very low to low levels is expected from 12-21 Sep. Another increase to R1-R2 levels is likely with the return of old Region 2673 on the visible disk on 22 Sep-05 Oct followed by a decrease to very low to low levels on 06-07 Oct.

The greater than 10 MeV proton event in progress is likely to continue through 14 Sep while the greater than 100 MeV proton event is likely to drop below the 1 pfu threshold by 12 Sep barring anyfurther enhancements. There is a chance for another greater than 10 MeV proton event above the 10 pfu (S1-Minor) level from 22 Sep-06 Oct due to the return of old Region 2673 to the visible disk.
The greater than 2 MeV electron flux at geosynchronous orbit is expected to be at high levels on 11-12 Sep, 14-20 Sep, and 28 Sep-07 Oct due to CH HSS influence.

Geomagnetic field activity is expected to be at unsettled to active levels on 11-17 Sep and 27 Sep-02 Oct with G1 (Minor) levels likely on 13-16 Sep and 27-29 Sep due to recurrent CH HSS activity. G2(Moderate) geomagnetic storm levels are likely on 13 Sep due to a combination of CH HSS activity and the possibility of a glancing blow enhancement from the 10 Sep CME.